Method of making thread rolling dies



July 13, 1943. H. c. ERDMAN 2,324,143

METHOD OF MAKING THREAD ROLLING DIES Filed Jan. 28, 1945 w i l l l l l /x f: i L W I INVENTOR.

Fl 6 HARVEY C 'kaMn/v 14% M M I flrrakusrs Patented July 13, 1943 METHOD OF IVIAKING THREAD ROLLING DIES Harvey O. Erdman, Shaker Heights, Ohio, as-

signor to The National Screw & Manufacturing Company, Cleveland, Ohio, a corporation of Ghio Application January 28, 1943, Serial No. 473,780

3 Claims.

This invention relates to a process of making thread rolling dies of the type disclosed in my application Serial No, 451,450, filed July 18, 1942.

In application Serial No. 451,450 there are disclosed dies not only for rolling the thread Oi threads on screws but for forming shoulders thereon which are continuations of the thread or threads on the screw, which shoulders extend for a distance at zero pitch and which are pro vided at their free ends with specially formed portions which prevent the reentry of the thread or threads when the screw is turned in the reverse direction,

With the dies of my application Serial No. 451,450 self-tapping combined screws and rivets, referred to as scrivets, are formed, these scrivets having V-threads. The shoulder to ing portions, which are located a distance from the head of the scrivet equivalent to thethicloness of the sheets to be fastened together, are also of V-formation and are of the same thickness, height, and proportions as the threads themselves.

The object of this invention is to provide an improved method by which rolling dies such as disclosed in my application Serial No. 451,450 may be formed.

The invention may be further briefly summarized as consisting in certain novel steps of the improved method which will be described in the specification and set forth in the appended claims.

In the accompanying sheet of drawings illus trating the method of forming the thread rolling dies,

Fig. 1 is a view of a hydraulic press shown in simplified form for stamping the shoulder form ing portions of the dies as continuations of the parallel milled grooves;

Fig. 2 is a face view of the stamp;

Fig. 3 is a view of one of the dies before the shoulder forming portions are applied;

Fig. 4 is a view of the same after the shoulder forming portions have been applied;

Fig. 5 is an enlarged view of a section of one of the completed. dies;

Fig. 6 is an edge view of the dies shown in the act of rolling threads on a scrivet; and

Fig. '7 is a View showing on an enlarged scale a scrivet employed for holding two work pieces together.

By reference to Figs. 3 and 4 which show the inner side of one of the dies l0 before and after the shoulder forming portions of the grooves have been applied, it will be seen that each die has thread rolling grooves composed of two portions including parallel V-portions Illa and shoulder forming V-portions Hlb which extend in a plane parallel to the edge or the die and at a suitable distance therefrom depending upon the thickness of the two pieces of stock or the two work sheets which are to be clamped together. As is customary, the die has on the starting point thereof deformations 25c which insure the desired or correct rolling of the scrivet blank between the dies. ihese dies form the scrivet El shown in Fig 7, the scrivet having a pair of V-threads Ma and each thread having a shoulder lib which is located a predetermined distance from the underside of the head lie to receive between the head the shoulders a pair of work sheets and to clamp them firmly between the head I I0 and the shoulders lib, as shown in Fig. i. It will be understood that the dies may be employed for rolling one, two, or more V-threads on the scrivet by varying the distance between the parallel portions lc'la of the grooves in the die. In Fig. 6 there are shown two dies is in the act of rolling threads on the scrivet H.

t will be noted by reference to Fig. '7 that the end of the shoulder portion is slightly downturned toward the free end of the shank of the scrivet. This is accomplished by suitably shaping the end of the groove forming the shoulder forming portion 19b of the die. This is shown clearly in Fig. 5 wherein the upper portion 10d of the end of the shoulder forming portion lllb is made shorter than the lower portion Hie which is preferably formed parallel with the portion Mia of the groove. It will be understood that these downturned portions of the threads at the ends of the shoulders of the scrivet assist the shoulders in effectively preventing the withdrawal of the scrivet by turning it in the reverse direction.

Referring now to the method of forming suitable extensions of the parallel grooves lfla in the die M so as to produce the shoulder forming portions Nib, it will be seen by reference to Fig. 3 that the die in its partially formed condition has simply straight parallel grooves Ifia milled therein whereas in Fig. 4 the grooves lfia have, in addition, shoulder forming portions lob formed therein at the correct distance from the edge of the die against which the head of the scrivet blank is to rest. This is accomplished by the use of a stamp i3 which is composed of a straight portion Isa, a shoulder forming portion [31) and a second straight portion which is formed as a continuation of the straight portion |3a (see Fig. 2). The portions l3a, I32), and I30 are formed as a V-rib which projects from the inset surface I4 of a stamping member Ma, The parts I32) and B0 are formed on a cylindrical piece I5 which is carefully fitted into a circular socket formed in the member Ma with the straight portion Be in perfect alignment with the portion I811.

In the use of this stamp there is first placed in the member Ma a liner l6 of a width such that the shoulder forming portion 13b is spaced the correct distance to space it from the top edge of the die a distance equivalent to the distance that the edge of the shoulder forming portion lUb is located from the head of the scrivet blank on which the thread is to be formed. Then each die I0 is placed in a holder I! shown in Fig. 1 and the parts Ma and I! with the die H] supported by the latter are placed in a hydraulic press with the V-rib of the stamp E3 in line with one of the straight grooves Mia and the press is closed with the straight portions of the ribs |3a and I30 fitted into one of the grooves Illa. This is repeated for each of the milled V-grooves la in the die l9 either by a hydraulic feeding device which feeds the die through the member I! or by manually positioning the stamp for each groove. Each time the press is closed the shoulder forming portion [Db and a short section of the groove Illa are stamped into the die as shown by the dotted lines l8 in Fig. 5, thus completing the thread forming groove of the die with the shoulder forming portion lab. The thread forming grooves of the companion die ID are formed in a similar manner.

Thus it will be seen that I have provided an improved method of forming on the die 10 straight portions 3a and stamped portions lflb which extend as continuations of the portions Illa parallel to the edge of the die so as to form on the scrivet at a suitable distance from the head thereof shoulder forming portions which extend for a distance at zero pitch.

While I have shown the preferred method of forming thread rolling dies, I do not desire to be confined to the precise details shown but aim in my claims to cover all modifications which do not involve a departure from the spirit and scope of the invention.

Having thus described my invention, I claim:

1. The method of forming a die for rolling threads on a scrivet with a thread portion or portions and a shoulder forming portion or portions spaced from the head of the scrivet, which comprises forming on the die parallel grooves, and stamping the shoulder forming portion as continuations of the parallel portions.

2. The method of forming a die for rolling threads on a scrivet with a thread portion or portions and a shoulder forming portion or portions spaced from the head of the scrivet, which comprises forming parallel grooves in the die and stamping as continuations of said grooves shoulder forming portions with short extensions of the parallel grooves.

3. The method of forming a die for rolling threads on a scrivet with a thread portion or portions and a shoulder forming portion or portions spaced from the head of the scrivet, which comprises forming parallel grooves in the die, and with a stamp having a rib with a straight portion which is adapted to be fitted into each of the parallel grooves of the die and having also a shoulder forming portion, forming the shoulder forming portion of the die as a continuation of each of said grooves with the straight portion of the rib of the stamp fitted successively into the parallel grooves formed in the die.

HARVEY C. ERDMAN. 

